This invention relates generally to circuit breakers, and, more particularly, this invention relates to interlocking cassettes for circuit breakers.
A current limiting circuit breaker is generally a high current circuit interrupting device capable of substantially limiting the duration and the intensity of current destined to flow in a circuit experiencing short circuit fault. To limit the duration and the intensity of short circuit currents, a circuit breaker must, within the shortest possible time, separate its contacts. This separation of the contacts is achieved by rapidly accelerating movable contact arms through an open gap. Upon the intense overcurrent conditions that result in the separation of the contacts, however, arcing often occurs between various parts in the circuit breaker. Arcing between the contacts is usually extinguished by passing the arc through an arc dissipating means. However, arcing may occur between other components of the circuit breaker as well.
Rotary contact arrangements are typically rotatably arranged on a support shaft between the fixed contact arms of the circuit breaker and function to interrupt the flow of current in the event that a short circuit occurs. A rotary contact arrangement employs a rotor and a pair of rotor springs to maintain contact between the movable contact arms and the fixed contact arms, thus maintaining a good electrical connection between the contacts. The compression forces provided by the rotor springs must be overcome when the contacts become separated and the circuit “blows open” due to the occurrence of opposing electrodynamic repulsion fields between the movable contact arm and the fixed contact arm.
Commonly, multiple contacts, each disposed within a cassette, are arranged within a circuit breaker system for protection of individual phases of current. The operating mechanism is positioned over one of the cassettes and generally connected to all of the cassettes in the system. The connection between the cassettes can become adversely affected under mechanical load of high stress short circuit conditions.